Abstract Nuclear power plant (NPP) is the final goal of the research and developments on the controlled nuclear fusion technologies. Small-diameter tubes, such as the mono-block tubes in divertors, are widely used in Tokamak fusion reactors and other NPPs. To ensure safety of controlled fusion reactors, pre-service and in-service non-destructive testing (NDT) for small-diameter tubes are of great importance. In view of this background, this paper proposes a new array eddy current testing (ECT) probe of high efficiency and detectability aiming for NDT of the small-diameter tubes. The excitation unit of the probe contains large coils of spiral configuration, and the pick-up unit consists of four small pancake coils with rectangle arrangement. The detection signal is taken as the specific difference of the outputs of the pick-up coils. The unique coil arrangement and signal mode can significantly reduce the wobbling noise due to both the probe lift-off change and inclination. The validity and efficiency of the probe configuration are verified in this paper through numerical simulation and experiments. A hybrid FEM-BEM code of A-φ formulation is adopted in the ECT signal simulation, and experiments are conducted by using simplified probe for plate specimen and an array ECT instrument. Both the simulation and experimental results reveal that the configuration of new array ECT probe is capable to detect both axial and circumferential crack in either inside or outside surface of a small-diameter tube.

中文翻译：

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用于检测托卡马克聚变装置中小直径管的新型阵列涡流检测探头

摘要 核电站（NPP）是可控核聚变技术研究和发展的最终目标。小直径管，例如偏滤器中的整体管，广泛用于托卡马克聚变反应堆和其他核电厂。为了确保可控聚变反应堆的安全，小直径管的服役前和服役中无损检测（NDT）非常重要。针对这一背景，本文针对小直径管子的无损检测，提出了一种高效、可检测的新型阵列涡流检测（ECT）探头。探头的励磁单元包含螺旋结构的大线圈，拾波单元由四个矩形排列的小扁平线圈组成。检测信号取为拾波线圈输出的特定差值。独特的线圈排列和信号模式可以显着降低由于探头提升变化和倾斜度引起的摆动噪声。本文通过数值模拟和实验验证了探针配置的有效性和有效性。ECT信号模拟采用A-φ公式的混合FEM-BEM代码，并使用简化的板试样探头和阵列ECT仪器进行实验。仿真和实验结果均表明，新型阵列ECT探头的配置能够检测小直径管内表面或外表面的轴向和圆周裂纹。本文通过数值模拟和实验验证了探针配置的有效性和有效性。ECT信号模拟采用A-φ公式的混合FEM-BEM代码，并使用简化的板试样探头和阵列ECT仪器进行实验。仿真和实验结果均表明，新型阵列ECT探头的配置能够检测小直径管内表面或外表面的轴向和圆周裂纹。本文通过数值模拟和实验验证了探针配置的有效性和有效性。ECT信号模拟采用A-φ公式的混合FEM-BEM代码，并使用简化的板试样探头和阵列ECT仪器进行实验。仿真和实验结果均表明，新型阵列ECT探头的配置能够检测小直径管内表面或外表面的轴向和圆周裂纹。